Testing: Fail CI build if local changes exist

package.json

@@ -159,7 +159,9 @@
 		"build": "npm run build:packages && cross-env NODE_ENV=production webpack",
 		"check-engines": "check-node-version --package",
 		"check-licenses": "concurrently \"wp-scripts check-licenses --prod --gpl2\" \"wp-scripts check-licenses --dev\"",
-		"ci": "concurrently \"npm run lint\" \"npm run test-unit:coverage-ci\"",
+		"precheck-local-changes": "npm run docs:build",
+		"check-local-changes": "git diff --exit-code > /dev/null || ( echo \"There are local uncommitted changes after one or both of 'npm install' or 'npm run docs:build'!\" && exit 1 );",
+		"ci": "concurrently \"npm run lint\" \"npm run test-unit:coverage-ci\" \"npm run check-local-changes\"",
 		"predev": "npm run check-engines",
 		"dev": "npm run build:packages && concurrently \"cross-env webpack --watch\" \"npm run dev:packages\"",
 		"dev:packages": "node ./bin/packages/watch.js",